Injection lance for uniformly injecting a steam/ammonia mixture into a fossil fuel combustion stream

ABSTRACT

An injection lance for injecting a homogeneous mixture of steam/ammonia gas into a furnace having a flue gas (combustion) stream moving therethrough to reduce nitrogen oxides therein. The lance includes an outer and an inner tube. The outer end of the inner tube is in communication with the outer tube while the outer end of the outer tube is in communication with a source of homogeneous steam/ammonia. The outer end of the inner tube sealably embraces the exterior surface of the lance feed tube so that the homogeneous steam/ammonia mixture being introduced into the outer tube passes towards the inner end of the lance between the annulus formed by the concentric outer and inner tubes. The homogeneous steam/ammonia mixture is passed into the annular space in the inner tube and then is discharged from the lance through discharge flow control nozzles or ports which extend from the interior of the inner tube to the exterior of the outer tube.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates generally to a nitrogen oxide (NOx) reduction process termed SNCR. More particularly, the injection lance of this invention is utilized for reducing NOx emitted from fossil fuel fired combustion processes. More particularly, the invention permits the uniform injection of a reagent (anhydrous, aqueous ammonia, or urea to ammonia conversion) and mixing steam into the furnace's flue gas combustion stream in a location which is between about 1600 to about 1900 degrees F. without the use of an additional temperature enhancing gas and about 1300 to about 1900 degrees F. with the use of a temperature enhancing gas.

[0003] 2. Description of the Related Art

[0004] Selective, non-catalytic nitrogen oxide reduction (SNCR) processes have been used for many years to reduce the oxides of nitrogen in combustion processes. SNCR has been used for the reduction of NOx to meet regulatory limits by a chemical process after combustion has already taken place. Numerous NOx reduction methods modify the combustion process itself by installing new burners and combustion-related equipment. On some boiler types, it is difficult, or impossible, to modify the combustion process equipment. It may also be desirable to lower NOx to levels below those obtainable by burner related equipment alone. In these cases, it may be desirable to reduce the NOx after it has been formed, rather than to attempt a different method of combustion.

[0005] In order to inject the SNCR reagent into the combustion stream, penetrations of the furnace must be accomplished. Penetrations require modifications to the furnace water wall tubes and the penetrations are expensive. Minimizing the number of boiler penetrations is important to the cost of installation on a SNCR system.

[0006] SNCR utilizes a reagent to create a localized reducing atmosphere to convert nitrogen oxide in the furnace to a nitrogen molecule. Inasmuch as this chemical reagent must be continuously injected into the boiler cavity, minimizing the cost of the reagent is important to the cost of operation of the furnace's SNCR system. It has been found that anhydrous ammonia is a more economical reagent than most competing reagents in the SNCR process. Due to the inherent personnel and community health risks associated with anhydrous ammonia; aqueous ammonia, or urea to ammonia conversion is sometimes utilized.

[0007] During the injection of the reagent into the furnace cavity, it is important that the reagent be uniformly mixed and thoroughly distributed in the furnace's flue gas stream temperature where the non-catalytic reduction reaction can occur. When injecting ammonia into the boiler, it is important that it not come into contact with an extremely hot surfaces (over approximately 900 degree F.), which will cause the ammonia to begin to thermally disassociate into nitrogen molecules, or will create even more nitrogen oxides when the disassociation is in the presence of an oxygen-rich atmosphere.

[0008] When ammonia is injected into the furnace flue gas stream as a vapor, the ammonia molecule is ready to begin the non-catalytic process without any additional vaporization which will reduce the formation of ammonia “slip” as an emission product. Previous testing has shown that ammonia also tends to create less global warming gases such as nitrous oxide (N₂O) and carbon dioxide (CO₂) then other reagents.

[0009] In those situations where the anhydrous, aqueous ammonia, or urea to ammonia conversion reagents are mixed with mixing air, it is important to reduce and limit the amount of mixing air, since the mixing air tends to increase the amount of available oxygen to combine with the disassociated nitrogen and create additional nitrogen oxides. Also, because the air is injected after the combustion process, it reduces the overall boiler efficiency.

[0010] Certain of the prior art utilizing reagent injection equipment does not permit the injection equipment to be inspected or modified while the boiler is in service. This is especially true on coal-fired furnaces, because the reagent is injected into a flue gas stream which contains “sticky” ash particles which could plug the variable, controllable injection ports and render the SNCR process ineffective.

[0011] U.S. Pat. No. 5,681,536 describes an injection lance for injecting a mixture of air and anhydrous ammonia into a boiler having a flue gas stream moving therethrough to reduce nitrous oxides therein. The lance includes outer, intermediate and inner tubes. The outer end of the inner tube is in communication with a source of anhydrous ammonia. The outer end of the outer tube is in communication with a source of mixing air. The outer end of the intermediate tube seals the exterior surface of the inner tube so that air being introduced into the outer tube passes toward the inner end of the lance between the outer and intermediate tubes. The mixing air and anhydrous ammonia are passed into the space between the inner tube and the intermediate tube and then are discharged through discharge nozzles from the interior of the intermediate tube to the exterior of the outer tube. This patent has the shortcoming that the use of heated air can cause a chemical reaction with ammonia to form byproducts of nitrogen (NO_(x)) and the mixing of air and ammonia internally is ineffective.

[0012] It is desirable to provide an improved injection lance for injecting a mixture of ammonia and steam into a furnace having a flue gas stream to reduce the nitrogen oxides therein providing optimized operating characteristics.

SUMMARY OF THE INVENTION

[0013] The present invention relates to an injection lance for injecting a homogeneous feed mixture, such as steam and ammonia, into a furnace having a flue gas stream moving therethrough to reduce the nitrogen oxides therein. The steam and ammonia are joined external to the injection lance to create a homogenous mixture to be introduced in the injection lance. By using steam, instead of mixing air, the thermal and oxidizing reduction of ammonia into NOx is drastically reduced or eliminated. The homogeneous steam/ammonia mixture which is preheated before entering the flue gas stream has a less detrimental effect on the overall furnace efficiency and has a lesser potential for droplet impingement corrosion on heat transfer surfaces. The term ammonia refers to a nitrogeneous compound such as anhydrous, aqueous, or urea to ammonia conversion ammonia.

[0014] The injection lance comprises an outer tube and an inner tube. The lance of the present invention comprises an elongated outer tube having closed inner and outer ends. The outer tube is in communication, adjacent its outer end, with a source of a feed mixture, such as a homogeneous steam/ ammonia mixture. An elongated inner tube, having inner and outer ends, is centrally positioned coaxially in the outer tube. The inner tube is in fluid communication, adjacent its outer end with the feed mixture. The outer end of the inner tube sealably embraces the lance feed tube inwardly of the location where the feed mixture enters the outer tube. The feed mixture passes between an annulus and formed by the outer tube and the inner tube and passes towards the inner end of the outer tube and into the open inner end of the inner tube. The inner tube can include an expansion mechanism provided thereon. A plurality of spaced-apart discharge ports or nozzles extend from the interior of the inner tube to the exterior of the outer tube so that the feed mixture present in the inner tube will be discharged into the flue gas stream substantially transversely with respect to the flow of gas.

[0015] The present invention provides an improved injection lance for injecting a homogeneous mixture of steam and ammonia into a combustion stream having a flue gas stream moving therethrough to reduce nitrogen oxides therein. The injection lance prohibits the ammonia from coming into contact with extremely hot surfaces in an air (oxygen-rich) atmosphere. The injection lance treats a major quantity of the furnace's flue gas with only a single boiler penetration.

[0016] The injection lance can be easily and automatically inserted or withdrawn from the furnace, such as by using standard industry devices, thus allowing for optimum temperature selection for ammonia injection, stopping the injection of the steam/ammonia mixture when the optimum temperature window does not exist in the furnace. This also allows inspection of the lance and its orifice ports, and repositioning (tuning/optimizing) of the variable, controllable orifice inserts along the length or radial axis of the lance without interrupting the combustion operation.

[0017] The injection lance of the present invention can be installed on the furnace without extensive modification thereof.

[0018] The invention will be more fully described by reference to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a plan view of the injection lance in accordance with the teachings of the present invention;

[0020]FIG. 2 is an elevation view of the injection lance of the present invention;

[0021]FIG. 3 is a perspective view of the injection lance of the present invention with a portion thereof cut away to more fully illustrate the invention;

[0022]FIG. 4 is an elongated sectional view taken through the injection lance;

[0023]FIG. 5 is a sectional view seen on Section A-A of FIG. 4;

[0024]FIG. 6 is a sectional view seen on detail 1 of FIG. 4;

[0025]FIG. 7A is a sectional view seen on section A-A of FIG. 6;

[0026]FIG. 7B is a sectional view seen on section B-B of FIG. 6;

[0027]FIG. 8 is a sectional view seen on detail 2 of FIG. 4;

[0028]FIG. 9 is a sectional view of an orifice port;

[0029]FIG. 10A is a sectional view of an orifice insert received in the orifice port;

[0030]FIG. 10B is a top plan view of the orifice insert;

[0031]FIG. 11A is a side sectional view of an orifice insert tool;

[0032]FIG. 11B is a bottom plan view of the orifice insert tool shown in FIG. 11A;

[0033]FIG. 11C is a top plan view of the orifice insert tool shown in FIG. 11A;

[0034]FIG. 12 is a sectional view seen on detail 3 of FIG. 4;

[0035]FIG. 13 is a sectional view seen on detail 4 of FIG. 4; and

[0036]FIG. 14 is a sectional view seen on detail 5 of FIG. 4.

DETAILED DESCRIPTION

[0037] Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts.

[0038]FIGS. 1-4 illustrate injection lance 10 in accordance with the teachings of the present invention. Injection lance 10 includes outer tube 18 having inner end 20 and outer end 22. Outer tube 18 includes interior surface 24 and exterior surface 26. Inner tube 28 is positioned centrally and coaxially with outer tube 18. Inner tube 28 has inner end 30 and outer end 32.

[0039] Outer end 32 of inner tube 28 is positioned outwardly of the furnace wall, as illustrated in FIG. 4, and is in communication with a source of feed mixture 29. Feed mixture 29 is adapted to be passed along the length of the lance feed tube 38 toward outer end 32 of inner tube 28. Feed mixture 29 can be a steam and a nitrogenous compound mixture. The nitrogenous compound can be ammonia (NH₃) or a compound that reacts to produce ammonia, such as urea. The source of ammonia can be anhydrous ammonia or aqueous ammonia. Feed mixture 29 can be homogenous. Feed mixture 29 can include additional gases, such as inert gases for optimizing the atmospheric condition. The use of an additional temperature enhancing gas reduces the operating condition to about 1300° F. to about 1900° F. Examples of additional gases include various hydrogen based gases such as hydrogen or methane.

[0040] For purposes of description, inner tube 28 will be described as including an interior surface 34 and an exterior surface 36, as shown in FIG. 5. Outer end 32 of inner tube 28 is provided with end seal 27, as illustrated in FIG. 4 and FIG. 6. Outer end 32 of inner tube 28 is sealably embracing by the means of end seal 27 at exterior surface 37 of lance feed tube 38. Inner end 40 of lance feed tube 38 is provided with a plurality of discharge openings 39, which causes the homogeneous steam/ammonia mixture ammonia to be forced in the direction of the arrows. Discharge opening can be provided at various locations in lance feed tube as shown in FIGS. 7A-7B. Feed mixture 29 exits discharge openings 39 and flows into annulus area 48 positioned between interior surface 24 of outer tube 18 and exterior surface 36 of inner tube 28, as shown in FIG. 6. Other means could be utilized as long as the feed mixture 29 is directed to annulus area 48 created by tube 18 and inner tube 28, once feed mixture 29 has been discharged from inner end 40 of lance feed tube 38.

[0041] As shown in FIG. 8, inner end 30 of inner tube 28 is spaced from inner end 20 of outer tube 18. Inner end 30 of inner tube 28 is open to provide a second passageway between annulus area 48 into the interior of inner tube 28.

[0042] A plurality of discharge orifice ports 54 are provided, as illustrated in FIGS. 4-5, and extend from interior surface 34 of inner tube 28 to exterior surface 26 of tube 18. Discharge orifice ports 54 are capable of accepting orifice inserts 55 or being plugged to control the amount and distribution of the feed mixture to optimize the removal of NOx from the flue gas stream. Discharge orifice ports 54 can have a nozzle shape, as shown in FIG. 3.

[0043] Discharge orifice ports 54 can have tapered sides 53, as shown in FIG. 9. Orifice inserts 55 can have a variable aperture 52 therein or provide a solid plug, as shown in FIGS. 10A-10B. Orifice inserts 55 can be inserted and removed from discharge ports 54. Orifice inserts 55 can have tapered sides 51 corresponding to tapered sides 53 of discharge orifice ports 54.

[0044] Orifice inserts 55 can be inserted or removed from discharge orifice ports using orifice insert tool 59 shown in FIGS. 11A-11C. Pins 60 of orifice insert tool 59 are inserted in apertures 57 of orifice insert. Pins 60 can be press fitted or replaceable to orifice insert tool 59. Top 61 of orifice insert tool 59 has protrusion 62. For example, protrusion 62 can have a hexagonal shape. Protrusion 62 can be rotated with a conventional tool such as a hex wrench for removal of orifice inserts 55 from orifice port 54.

[0045] After insertion of orifice insert tool 59 into insert 55, inner tube 28 can be provided with a plurality of slip tubes 56, as shown in FIG. 3 and FIG. 12. Slip tubes 56 permit movement of inner tube 28 with respect to outer tube 18. Slip tubes 56 are preferably provided inasmuch as outer tube 18 is exposed to a greater temperature resulting from exposure to the furnace than inner tube 28 resulting in greater expansion of outer tube 18. Slip tubes 56 allow expansion of inner tube 28 to be comparable to expansion of outer tube 18. It should be noted, however, that slip tubes 56 may not be needed for relatively short injection lances 10.

[0046] Outer tube 18 is provided with mating flange 64 which includes a reducing fitting 65 to enable the injection lance 10 to be retrofitted to a retract mechanism, as shown in FIG. 13. For example, mating flange 64 can be a conventional mechanism as manufactured by Clyde Bergmann as a lance flange. Retract mechanisms can be a conventional mechanism for coupling to mating flange 64.

[0047] Injection lance 10 extends through the opening 70 in furnace water wall 72 of furnace 73, as shown in FIG. 14. Sootblower drive 74 is adapted to move the injection lance 10 inwardly into the flue gas stream, outwardly, or rotationally therefrom when it is desired to control the injection for NOx control, inspect the condition of the lance, when it is desired to perform maintenance thereon, or to reconfigure orifice inserts 55 to achieve optimum NOx reduction and minimum ammonia slip performance.

[0048] In operation, feed mixture 29 is introduced into inner end 30 of inner tube 28 after traveling thru annulus area 48 formed by outer tube 18 and inner tube 28. Feed mixture 29 is then introduced to the interior area passageway of inner tube 28. Feed mixture 29 is then discharged through discharge orifice ports 54 and orifice inserts 55 into the flue gas stream where the mixture reacts with the nitrogen oxides therein to reduce the level thereof.

[0049] The longitudinal axis of injection lance 10 can be disposed transversely with respect to the flow of the flue gases whether the flue gases are moving horizontally, vertically or a combination thereof. Discharge orifice ports 54 are positioned on injection lance 10 so that the feed mixture is directed into the flue gases at an optimum angle thereto. Thus, if the flue gases are moving vertically upwardly through the furnace, the longitudinal axes of the discharge orifice ports 54 will be horizontally disposed. Conversely, if the flue gases are moving horizontally through the furnace, the longitudinal axes of discharge orifice ports 54 will be vertically disposed. If the flue gas is moving at an angle through the furnace, the longitudinal axes of discharge orifice ports 54 can be adjusted to the optimum angle thereto.

[0050] It is also important to note that inner tube 28 is somewhat insulated from the hot combustion gases due to the fact that outer tube 18 is positioned around the inner tube. Thus, the feed mixture is removing from outer tube 18 the heat of the flue gas until the feed mixture is discharged into the gas stream. Injection lance 10, by its design, provides a homogeneous mixture which is approximately the same temperature at all discharge orifice ports 54 along the length of injection lance 10.

[0051] It is to be under stood that the above-described embodiments are illustrative of only a few of the many possible specific embodiments which can represent applications of the principles of the invention. Numerous and varied other arrangements can be readily devised in accordance with these principles by those skilled in the art without departing from the spirit and scope of the invention. 

We claim:
 1. An injection lance comprising: an outer tube having closed inner and outer ends; an inner tube centrally positioned in said outer tube, said inner tube having inner and outer ends, said inner end of said inner tube being open, said inner end of said inner tube being spaced apart from said inner end of said outer tube, said inner tube being in fluid communication with a feed mixture; an interior surface of said outer tube and an exterior surface of said inner tube forming an annulus for defining a first passageway; an interior surface of said inner tube defining a second passageway between said annulus and an interior of said inner tube through said inner end of said inner tube; and at least one discharge orifice port extending from the interior surface of said inner tube to the exterior surface of said outer tube, wherein said feed mixture passes from said outer end of said inner tube towards said inner end of said outer tube in said first passageway and then passes into said interior of said inner tube in said second passageway and is discharged from said discharge ports.
 2. The injection lance of claim 1 wherein said feed mixture is a mixture of steam and ammonia.
 3. The injection lance of claim 2 wherein said feed mixture is homogenous.
 4. The injection lance of claim 2 wherein said ammonia is selected from the group consisting of anhydrous ammonia, aqueous ammonia or urea conversion ammonia.
 5. The injection lance of claim 2 wherein the feed mixture further comprises an additional gas to lower the optimum reaction temperature.
 6. The injection lance of claim 5 wherein said additional gas is hydrogen or methane.
 7. The injection lance of claim 1 further comprising a lance feed tube receiving said feed mixture and a seal between said lance feed tube and said inner tube.
 8. The injection lance of claim 7 wherein said lance feed tube includes a plurality of openings to discharge said feed mixture into said first passageway.
 9. The injection lance of claim 1 wherein said inner tube includes at least one slip tube to absorb thermal expansion between said outer tube and said inner tube therein.
 10. The injection lance of claim 1 wherein said inner tube includes a plurality of slip tubes to absorb thermal expansion between said outer tube and said inner tube therein.
 11. The injection lance of claim 1 further comprising at least one orifice insert being received in said at least one discharge orifice port.
 12. The injection lance of claim 11 wherein said orifice insert has an aperture therein.
 13. The injection lance of claim 12 wherein said aperture is variable.
 14. The injection lance of claim 11 wherein said orifice insert is solid.
 15. The injection lance of claim 11 wherein said discharge orifice port and said orifice insert have corresponding tapered sides.
 16. The injection lance of claim 11 wherein said orifice insert is removable.
 17. The injection lance of claim 16 wherein said orifice insert includes at least one aperture for receiving a pin at one end of an orifice insert tool, said orifice insert tool including apertures at a second end thereof.
 18. The injection lance of claim 1 wherein said outer tube further comprises a mating flange and reducing fitting at said outer end of said outer tube.
 19. The injection lance of claim 2 wherein the steam creates an oxygen-deprived atmosphere within said injection lance to retard or hinder the thermal oxidation of the ammonia vapor normally found in a high temperature oxygen rich atmosphere.
 20. A combination comprising: a furnace or combustion process having a flue gas stream moving therethrough; an outer tube having closed inner and outer ends; an inner tube centrally positioned in said outer tube, said inner tube having inner and outer ends, said inner end of said inner tube being open, said inner end of said inner tube being spaced apart from said inner end of said outer tube, said inner tube being in fluid communication with a feed mixture; an interior surface of said outer tube and an exterior surface of said inner tube forming an annulus for defining a first passageway; an interior surface of said inner tube defining a second passageway between said annulus and an interior of said inner tube through said open inner end of said inner tube; and at least one discharge orifice port extending from the interior surface of said inner tube to the exterior surface of said outer tube, wherein said feed mixture passes from said outer end of said inner tube towards said inner end of said outer tube in said first passageway and then passes into said interior of said inner tube in said second passageway and is discharged from said discharge ports.
 21. The combination of claim 20 wherein said feed mixture is a mixture of steam and ammonia.
 22. The combination of claim 21 wherein said feed mixture is homogenous.
 23. The combination of claim 21 wherein said ammonia is selected from the group consisting of anhydrous ammonia, aqueous ammonia or urea conversion ammonia.
 24. The combination of claim 21 wherein the feed mixture further comprises an additional gas to lower the optimum reaction temperature.
 25. The combination of claim 24 wherein said additional gas is hydrogen or methane.
 26. The combination of claim 20 further comprising a lance feed tube receiving said feed mixture, and a seal between said lance feed tube and said inner tube.
 27. The combination of claim 26 wherein said lance feed tube includes a plurality of openings to discharge said feed mixture into said first passageway.
 28. The combination of claim 20 wherein said inner tube includes at least one slip tube to absorb thermal expansion between said outer tube and said inner tube therein.
 29. The combination of claim 20 wherein said inner tube includes a plurality of slip tubes to absorb thermal expansion between said outer tube and said inner tube therein.
 30. The combination of claim 20 further comprising at least one orifice insert being received in said at least one discharge orifice port.
 31. The combination of claim 30 wherein said orifice insert has an aperture therein.
 32. The combination of claim 30 wherein said aperture is variable.
 33. The combination of claim 30 wherein said orifice insert is solid.
 34. The combination of claim 30 wherein said discharge orifice port and said orifice insert have corresponding tapered sides.
 35. The combination of claim 20 wherein said orifice insert is removable.
 36. The combination of claim 35 wherein said orifice insert includes at least one aperture for receiving a pin at one end of an orifice insert tool, said orifice insert tool including apertures at a second end thereof.
 37. The combination of claim 20 wherein said outer tube further comprises a mating flange and reducing fitting at said outer end of said outer tube.
 38. The combination of claim 20 further comprising a mechanical retract/insertion mechanism for moving said lance into said furnace and outwardly therefrom attached to said mating flange.
 39. The combination of claim 38 wherein said mechanical insertion/retract mechanism allows for the rotation of the inserted said injection lance about its centroidal axis to allow for optimizing its performance.
 40. The combination of claim 21 wherein the steam creates an oxygen-deprived atmosphere within said injection lance to retard or hinder the thermal oxidation of the ammonia vapor normally found in a high temperature oxygen rich atmosphere.
 41. The combination of claim 20 wherein said furnace or combustor includes a vertical or horizontal wall and wherein said injection lance extends substantially horizontally or vertically through said furnace wall.
 42. The combination of claim 20 wherein said lance has a longitudinal axis which is substantially transversely disposed with respect to the direction of movement of the flue gas stream moving through said furnace.
 43. The combination of claim 42 wherein said discharge orifice ports are oriented on said lance so that said feed mixture is discharged into the flue gas stream substantially transversely with respect thereto.
 44. The combination of claim 42 wherein said discharge orifice ports are oriented on said lance so that said feed mixture is discharged into the flue gas stream but can be located to discharge in an orientation to achieve optimized performance.
 45. The combination of claim 20 wherein the spacing of said inner tube with respect to said outer tube is constructed and arranged such that said feed mixture being discharged into the flue gas stream will be approximately the same along the length of said lance.
 46. The combination of claim 20 wherein said annulus and the passing flow of said feed stream cools said outer tube from the flue gas.
 47. A method for uniformly injecting a feed stream into a fuel combustion stream comprising the steps of: mixing steam with ammonia to form said feed stream; introducing said feed stream into an injection lance, said injection lance comprising an outer tube having closed inner and outer ends; an inner tube centrally positioned in said outer tube, said inner tube having inner and outer ends, said inner end of said inner tube being open, said inner end of said inner tube being spaced apart from said inner end of said outer tube said inner tube being in fluid communication with said feed mixture; an interior surface of said outer tube and an exterior surface of said inner tube forming an annulus for defining a first passageway; an interior surface of said inner tube defining a second passageway between said annulus and an interior of said inner tube through said open inner end of said inner tube; and at least one discharge orifice port extending from the interior surface of said inner tube to the exterior surface of said outer tube, said feed mixture passes from said outer end of said inner tube towards said inner end of said outer tube in said first passageway and then passes into said interior of said inner tube in said second passageway; and discharging said feed stream from said discharge ports into said fossil fuel combustion stream.
 48. The method of claim 47 wherein said feed mixture is a mixture of steam and ammonia.
 49. The method of claim 48 wherein said feed mixture is homogenous.
 50. The method of claim 48 wherein said ammonia is selected from the group consisting of anhydrous ammonia, aqueous ammonia or urea conversion ammonia.
 51. The method of claim 48 wherein the feed mixture further comprises an additional gas to lower the optimum reaction temperature.
 52. The injection lance of claim 51 wherein said additional gas is hydrogen or methane.
 53. The method of claim 47 wherein said lance further comprises a lance feed tube receiving said feed mixture, and a seal between said lance feed tube and said inner tube.
 54. The method of claim 47 wherein said lance feed tube includes a plurality of openings to discharge said feed mixture into said first passageway.
 55. The method of claim 47 wherein said inner tube includes at least one slip tube to absorb thermal expansion between said outer tube and said inner tube therein.
 56. The method of claim 47 wherein said lance further comprises: at least one orifice insert being received in said at least one discharge orifice port.
 57. The method of claim 47 wherein said lance further comprises wherein said orifice insert has an aperture therein.
 58. The method of claim 47 wherein said lance further comprises wherein the steam creates an oxygen-deprived atmosphere within said injection lance to retard or hinder the thermal oxidation of the ammonia vapor normally found in a high temperature oxygen rich atmosphere. 